Photobleaching is a significant limiting factor in live cell studies, not only because it ultimately limits the amount of information available to the researcher but because it is often associated with deleterious energy input into the specimen. Presently measurements of photobleaching parameters are few and contradictory. We have devised a simple and reproduceable method for measuring fluorophore photobleaching rates by examining fluorescence yields as a function of scan speed. Because laser scan rates are fast ((sec/focal volume), fluorophores can be examined under the rapidly diffusing aqueous conditions that exist in live cell studies. A manuscript describing these results is currently under preparation.